1. Field of the Invention
The present invention generally relates to a code reading device and method suitable to an exposure apparatus and a device manufacturing method, wherein the exposure apparatus is preferably used in a lithography process for manufacturing micro-devices.
2. Description of the Related Art
A semiconductor manufacturing apparatus normally has an automated transferring system for transferring (i) a substrate (e.g., a reticle, a mask or a wafer) or (ii) a carrier cassette, which stores the substrate, between apparatuses or within the apparatus. The automated apparatus prevents contaminated particles from adhering to the substrate, and provides the ability to increase productivity.
In that transferring system, for the purpose of reliable administration of the substrates, providing the ability to discriminate and provide the correct substrate in each process, a discrimination code pattern (e.g., a barcode), having information for discriminating one substrate from other substrates, is printed on the substrate. At least one of a correction, a registration, an inquiry or a confirmation of substrate data is performed by reading the code on the substrate in each process.
Since the substrate (e.g., a reticle) is normally made of transparent glass and the code is covered with an anti-reflection film to avoid unwanted effects during exposure, a contrast between the non-transparent pattern portion of the code and the transparent portion of the glass may become lower, and that would disturb code reading. In order to address the above challenge, Japanese Laid-Open Patent Application No. 7-66118 discloses a transparent-type code reading device that has an illuminator and a detector, being separate from each other, to read the code by illuminating the code and detecting light passed through the code onto the substrate.
In recent years, new advancements in technology, such as a modified illumination arrangement and a phase-shift mask, to increase resolution, have been developing to allow ultra-precise resolution of line widths thinner than an exposure light wavelength. Simultaneously, a so-called halftone mask, which has circuit patterns having half transparency, has appeared.
However, in the above-mentioned halftone mask, if the discrimination code pattern is formed beside the circuit patterns in the same manner as the circuit patterns, the code pattern has a high transparency, and a contrast between pattern-formed portions and non-pattern-formed portions becomes lower as the pattern transparency increases. As a result, it would become unsuitable for reading, and may cause a reading error.
The present invention is provided to overcome the challenges discussed above and a general object of the invention is to provide an improved code reading device, and an exposure apparatus and a semiconductor manufacturing method utilizing the improved code reading device.
It is a still more specific object of the invention to provide a reliable device being capable of reading a code formed on a substrate, with stability, even though the code pattern has a high transparency or even though the contrast is not so high.
According to one aspect of the present invention, a code reading device comprises an illuminator which illuminates a code on a substrate with light, a reflector which reflects the light to allow the light to pass through the code on the substrate at least two times, and a detector which detects the reflected light to read the code on the substrate.
According to another aspect of the present invention, an exposure apparatus comprises a storage unit which stores a plurality of substrates, wherein the substrate is one of a photomask, a reticle, a wafer and a glass plate, an exposure unit which performs exposure operations with the substrate, a code reading device and a handler. The code reading device has an illuminator which illuminates with light a code formed on one of the plurality of substrates, a reflector which reflects the light to allow the light to pass through the code on the substrate at least two times, and a detector which detects the reflected light to read the code on the substrate. The handler handles a respective one of the substrates to move the substrate to a reading position for reading of the code by the detector.
According to yet another aspect of the present invention, a semiconductor manufacturing method comprises the steps of performing exposure operations with a substrate, wherein the substrate is one of a photomask, a reticle, a wafer and a glass plate, and the substrate has an exposure pattern and a code formed thereon, illuminating the code formed on the substrate with light to read the code and administer a respective substrate, allowing the light to pass through the code on the substrate at least two times so as to increase a reading contrast of the code, and reading the illuminated code on the substrate.